JavaScript实现简易网格布局与坐标计算

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">  <html>    <head>      <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />      <title>Untitled Document</title>      <style type="text/css">        *{margin:0px;padding:0px}        table#tab{          border:solid #ccc;          border-width:1px 0px 0px 1px;        }        table#tab tr td{          border:solid #ccc;          border-width:0px 1px 1px 0px;        }      </style>          </head>    <body>      <div id="aa">            </div>    </body>  </html> 

[Ctrl+A 全选 注:引入外部Js需再刷新一下页面才能执行]